Here (machine translation) is a DIY single-layer version of the Arduino Leonardo. The blogger goes into detail on how to build one yourself. Everything is covered from preparing and etching your own DIY board, to fine pitch soldering of the ATmega32u4 IC. Once you have built your board, they show you how to upload a bootloader into the microcontroller.
The Arduino Leonardo is a new platform from the Arduino team that uses the ATmega32U4 uC with built in USB capability. This eliminates the need for the expensive FTDI USB-to-serial ICs and keeps the costs down.